With nearly two dozen regulators examining equipment and processes at the troubled Browns Ferry Nuclear Plant this week and next, TVA said Thursday it has made "continuous, sustainable improvements" to remove Browns Ferry from the worst performance rating of any U.S. nuclear plant by the Nuclear Regulatory Commission.

"We're not where we want to be, but we are making progress and headed in the right direction," utility spokesman Mike Bradley said after a briefing by NRC officials.

The NRC has dispatched 23 inspectors to Browns Ferry to assess the plant and its safety systems and culture.

The inspection, one of the most thorough of any nuclear plant, comes more than a year and a half after the NRC cited the Unit 1 reactor at the Browns Ferry plant for a red-level violation. The red finding is the most severe citation short of ordering the plant to shut down. Browns Ferry is only the fifth plant to be "red-flagged" and is the only one of the 103 operating U.S. reactors under the red finding.

In the fall of 2011, NRC officials discovered a valve was stuck shut on an emergency cooling system that could have been used during a fire at the plant. Bill Jones, deputy director of the NRC's division of reactor projects in Atlanta, said the valve failure went undetected for nearly a year and a half and highlighted a lack of attention to detail and procedures at TVA's biggest power plant.

"When we took into account the failure of this valve and the risk from a possible fire, we determined the event was of very high significance and that is why we issued the red finding," he said.

TVA budgeted $138 million this fiscal year to install safety systems and improve staff training and procedures at Browns Ferry, Bradley said.

The utility also upgraded the cable systems and other plant equipment to comply with fire regulations so workers no longer will have to staff fire watches and take other measures to meet NRC fire standards.

Jones said he expects the NRC to issue its findings from the current inspection program at Browns Ferry in late June. He said the NRC could either extend the red finding, order other improvements or lift the citation.

Contact Dave Flessner at dflessner@timesfreepress.com or at 423-757-6340.